Implement __SCOPE__ (#1845)

man/rgbasm.5

@@ -1729,6 +1729,7 @@ The following symbols are defined by the assembler:
 .It Dv @ Ta Ic EQU Ta PC value (essentially, the current memory address)
 .It Dv . Ta Ic EQUS Ta The current global label scope
 .It Dv .. Ta Ic EQUS Ta The current local label scope
+.It Dv __SCOPE__ Ta Ic EQUS Ta The innermost current label scope level (empty, ".", or "..")
 .It Dv _RS Ta Ic = Ta _RS Counter
 .It Dv _NARG Ta Ic EQU Ta Number of arguments passed to macro, updated by Ic SHIFT
 .It Dv __ISO_8601_LOCAL__ Ta Ic EQUS Ta ISO 8601 timestamp (local)

src/asm/symbol.cpp

@@ -39,6 +39,7 @@ static Symbol const *localScope = nullptr;  // Current section's local label sco
 
 static Symbol *PCSymbol;
 static Symbol *NARGSymbol;
+static Symbol *SCOPESymbol;
 static Symbol *globalScopeSymbol;
 static Symbol *localScopeSymbol;
 static Symbol *RSSymbol;
@@ -67,6 +68,19 @@ static int32_t NARGCallback() {
 	}
 }
 
+static std::shared_ptr<std::string> SCOPECallback() {
+	if (localScope) {
+		return std::make_shared<std::string>("..");
+	} else if (globalScope) {
+		return std::make_shared<std::string>(".");
+	} else {
+		if (!sect_GetSymbolSection()) {
+			error("`__SCOPE__` has no value outside of a section");
+		}
+		return std::make_shared<std::string>("");
+	}
+}
+
 static std::shared_ptr<std::string> globalScopeCallback() {
 	if (!globalScope) {
 		error("`.` has no value outside of a label scope");
@@ -296,6 +310,10 @@ Symbol *sym_FindScopedValidSymbol(std::string const &symName) {
 	if (sym == localScopeSymbol && !localScope) {
 		return nullptr;
 	}
+	// `__SCOPE__` has no value outside of a section
+	if (sym == SCOPESymbol && !sect_GetSymbolSection()) {
+		return nullptr;
+	}
 
 	return sym;
 }
@@ -683,6 +701,11 @@ void sym_Init(time_t now) {
 	localScopeSymbol->data = localScopeCallback;
 	localScopeSymbol->isBuiltin = true;
 
+	SCOPESymbol = &createSymbol("__SCOPE__"s);
+	SCOPESymbol->type = SYM_EQUS;
+	SCOPESymbol->data = SCOPECallback;
+	SCOPESymbol->isBuiltin = true;
+
 	RSSymbol = sym_AddVar("_RS"s, 0);
 	RSSymbol->isBuiltin = true;
 

test/asm/scope-level.asm

@@ -0,0 +1,27 @@
+assert !def(__SCOPE__)
+
+section "test", rom0
+
+assert !def(.)
+assert !def(..)
+assert #__SCOPE__ === ""
+
+Alpha.local1:
+assert !def(.)
+assert #.. === "Alpha.local1"
+assert #__SCOPE__ === ".."
+
+Beta:
+assert #. === "Beta"
+assert !def(..)
+assert #__SCOPE__ === "."
+
+Alpha.local2:
+assert #. === "Beta"
+assert #.. === "Alpha.local2"
+assert #__SCOPE__ === ".."
+
+.newLocal:
+assert #. === "Beta"
+assert #.. === "Beta.newLocal"
+assert #__SCOPE__ === ".."